A gunman opened fire near the White House on Saturday evening, with US Secret Service agents killing the assailant in a shoot-out during which a bystander was also struck, authorities said.

US President Donald Trump was at the White House at the time as he worked to negotiate a deal with Iran, but was not affected by the incident, Secret Service communications chief Anthony Guglielmi said in a statement.

The confrontation took place just after 6pm (local time) when a man near the White House security perimeter “pulled a weapon from his bag and began firing”.

“Secret Service Police returned fire striking the suspect who was transported to an area hospital where he was pronounced deceased. During the shooting, one bystander was also struck by gunfire,” Guglielmi said, without giving details on the bystander’s condition.

No Secret Service officers were hurt.

“Thank you to our great Secret Service and Law Enforcement for the swift and professional action taken this evening against a gunman near the White House, who had a violent history and possible obsession with our Country’s most cherished structure,” Trump said on social media early on Sunday.